Semiconductor device having a necked semiconductor  body and method of forming semiconductor bodies of varying width

ABSTRACT

Semiconductor devices having necked semiconductor bodies and methods of forming semiconductor bodies of varying width are described. For example, a semiconductor device includes a semiconductor body disposed above a substrate. A gate electrode stack is disposed over a portion of the semiconductor body to define a channel region in the semiconductor body under the gate electrode stack. Source and drain regions are defined in the semiconductor body on either side of the gate electrode stack. Sidewall spacers are disposed adjacent to the gate electrode stack and over only a portion of the source and drain regions. The portion of the source and drain regions under the sidewall spacers has a height and a width greater than a height and a width of the channel region of the semiconductor body.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor devicesand processing and, in particular, semiconductor devices having neckedsemiconductor bodies and methods of forming semiconductor bodies ofvarying width.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory or logic devices on achip, lending to the fabrication of products with increased capacity.The drive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

In the manufacture of integrated circuit devices, multi-gatetransistors, such as fin-FET and tri-gate transistors, have become moreprevalent as device dimensions continue to scale down. In conventionalprocesses, fin-FET and tri-gate transistors are generally fabricated oneither bulk silicon substrates or silicon-on-insulator substrates. Insome instances, bulk silicon substrates are preferred due to their lowercost and because they may enable a less complicated fin-FET and tri-gatefabrication process. In other instances, silicon-on-insulator substratesare preferred because of the improved short-channel behavior of fin-FETand tri-gate transistors.

Scaling multi-gate transistors has not been without consequence,however. As the dimensions of these fundamental building blocks ofmicroelectronic circuitry are reduced and as the sheer number offundamental building blocks fabricated in a given region is increased,the constraints on the external resistance (R_(ext)) during performanceof such devices have become overwhelming. Many different techniques havebeen attempted to improve R_(ext) of transistors including improvedcontact metals, increased activation of dopant and lowered barriersbetween the semiconductor and contact metal. However, significantimprovements are still needed in the area of R_(ext) reduction.

SUMMARY

Embodiments of the present invention include semiconductor deviceshaving necked semiconductor bodies and methods of forming semiconductorbodies of varying width.

In an embodiment, a semiconductor device includes a semiconductor bodydisposed above a substrate. A gate electrode stack is disposed over aportion of the semiconductor body to define a channel region in thesemiconductor body under the gate electrode stack. Source and drainregions are defined in the semiconductor body on either side of the gateelectrode stack. Sidewall spacers are disposed adjacent to the gateelectrode stack and over only a portion of the source and drain regions.The portion of the source and drain regions under the sidewall spacershas a height and a width greater than a height and a width of thechannel region of the semiconductor body.

In another embodiment, a method of fabricating a semiconductor deviceincludes forming a semiconductor body above a substrate. A gateelectrode stack is formed over a portion of the semiconductor body todefine a channel region in the semiconductor body under the gateelectrode stack and source and drain regions in the semiconductor bodyon either side of the gate electrode stack. Sidewall spacers are formedadjacent to the gate electrode stack and over only a portion of thesource and drain regions. The portion of the source and drain regionsunder the sidewall spacers has a height and a width greater than aheight and a width of the channel region of the semiconductor body.

In another embodiment, a method of fabricating a semiconductor deviceincludes forming a hardmask pattern above a substrate. The hardmaskpattern includes a first region of fin forming features, each of a firstwidth. The hardmask pattern also includes a second region of fin formingfeatures, each of a second width approximately equal to the first width.Subsequently, a resist layer is formed and patterned to cover the secondregion and expose the first region. Subsequently, the fin formingfeatures of the first region are etched to form thinned fin formingfeatures, each of a third width less than the second width.Subsequently, the resist layer is removed. Subsequently, the hardmaskpattern is transferred to the substrate to form a first region of fins,each of the third width, and to form a second region of fins, each ofthe second width. Subsequently, semiconductor devices are formed fromthe fins of the first and second regions.

In another embodiment, a method of fabricating a semiconductor deviceincludes forming a hardmask pattern above a substrate. The hardmaskpattern includes a first region of fin forming features, each of a firstwidth. The hardmask pattern also includes a second region of fin formingfeatures, each of a second width approximately equal to the first width.Subsequently, the hardmask pattern is transferred to the substrate toform a first region of fins, each of the first width, and to form asecond region of fins, each of the second width. Subsequently, a resistlayer is formed and patterned to cover the second region of fins and toexpose the first region of fins. Subsequently, the fins of the firstregion are etched to form thinned fins, each of a third width less thanthe second width. Subsequently, the resist layer is removed.Subsequently, semiconductor devices are formed from the fins of thefirst and second regions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a plan view of a semiconductor device having anecked semiconductor body, in accordance with an embodiment of thepresent invention.

FIG. 1B illustrates a cross-sectional view of the semiconductor deviceof FIG. 1A, as taken along the a-a′ axis, in accordance with anembodiment of the present invention.

FIG. 1C illustrates a cross-sectional view of the semiconductor deviceof FIG. 1A, as taken along the b-b′ axis, in accordance with anembodiment of the present invention.

FIG. 2A illustrates a plan view of a semiconductor device having anecked semiconductor body, in accordance with an embodiment of thepresent invention.

FIG. 2B illustrates a plan view of another semiconductor device having anecked semiconductor body, in accordance with another embodiment of thepresent invention.

FIG. 2C illustrates a plan view of another semiconductor device having anecked semiconductor body, in accordance with another embodiment of thepresent invention.

FIG. 3 illustrates a process flow in a method of fabricating asemiconductor device having a necked semiconductor body, in accordancewith an embodiment of the present invention.

FIG. 4 illustrates a process flow in a method of fabricating asemiconductor device having a necked semiconductor body, in accordancewith an embodiment of the present invention.

FIG. 5A includes a plot of drive current gain (as % Idsat gain) as afunction of silicon channel thickness (in microns) of a semiconductordevice having a necked semiconductor body versus a semiconductor devicewithout a necked semiconductor body, in accordance with an embodiment ofthe present invention.

FIG. 5B includes a plot of drive current gain (as % Idlin gain) as afunction of silicon channel thickness (in microns) of a semiconductordevice having a necked semiconductor body versus a semiconductor devicewithout a necked semiconductor body, in accordance with an embodiment ofthe present invention.

FIG. 6 illustrates a process flow in a method of fabricatingsemiconductor devices having with semiconductor bodies of varying width,in accordance with an embodiment of the present invention.

FIG. 7 illustrates a process flow in a method of fabricatingsemiconductor devices having with semiconductor bodies of varying width,in accordance with an embodiment of the present invention.

FIG. 8 illustrates a computing device in accordance with oneimplementation of the invention.

DETAILED DESCRIPTION

Semiconductor devices having necked semiconductor bodies and methods offorming semiconductor bodies of varying width are described. In thefollowing description, numerous specific details are set forth, such asspecific integration and material regimes, in order to provide athorough understanding of embodiments of the present invention. It willbe apparent to one skilled in the art that embodiments of the presentinvention may be practiced without these specific details. In otherinstances, well-known features, such as integrated circuit designlayouts, are not described in detail in order to not unnecessarilyobscure embodiments of the present invention. Furthermore, it is to beunderstood that the various embodiments shown in the Figures areillustrative representations and are not necessarily drawn to scale.

One or more embodiments of the present invention are targeted atsemiconductor devices having (1) a different fin width in an activechannel region versus fin width underneath a spacer, (2) an integratedcircuit with at least two different fin widths in different activechannels on the same die, (3) a patterning process to define twodifferent fin widths prior to actual fin etch, (4) a patterning processto define two different fin widths after a sacrificial dummy gateremoval process, or combinations thereof. One or more embodiments aretargeted at improving the drive current of devices such as transistorsand to build circuits that have low idle power and high activeperformance.

The width of a fin in a FinFET impacts the threshold voltage (Vt) andthe external resistance of the device. For high performance devices itmay be beneficial to have a relatively wider fin with higher Vt andlower resistance. For low-power devices, the opposite is true.Currently, the process has to be optimized for one of these devices. Itmay be beneficial to have the best performance for both devices tooptimize product power performance. For example, low-power devices aregenerated with additional well doping leading to higher Vt and higherjunction leakage which degrade drive currents, especially at low powersupply voltage. Alternatively the process is optimized for low-powerdevices leading to degraded drive current of the high-performancedevices. Embodiments of the present invention may enable thesimultaneous optimization of high performance and low power devices byeither offering two different devices on the same die or by a devicethat has both low Vt and low external resistance.

In a first aspect, a semiconductor device having a necked semiconductorbody and methods of forming a semiconductor device having a neckedsemiconductor body are provided. Such a transistor structure has adifferent fin width in the channel and in the fin region underneath thespacer. A necked fin may improve the tradeoff between short channeleffect improvement and external resistance as the fin CD is scaled,improving the drive current of the best device.

In an example, FIG. 1A illustrates a plan view of a semiconductor devicehaving a necked semiconductor body, in accordance with an embodiment ofthe present invention. FIG. 1B illustrates a cross-sectional view of thesemiconductor device of FIG. 1A, as taken along the a-a′ axis, inaccordance with an embodiment of the present invention. FIG. 1Cillustrates a cross-sectional view of the semiconductor device of FIG.1A, as taken along the b-b′ axis, in accordance with an embodiment ofthe present invention.

Referring to FIGS. 1A-1C, a semiconductor device 100 includes asemiconductor body 104 disposed above a substrate 102. A gate electrodestack 106 is disposed over a portion of the semiconductor body 104 todefine a channel region 108 in the semiconductor body 104 under the gateelectrode stack 106. Source and drain regions 110 are defined in thesemiconductor body 104 on either side of the gate electrode stack 106.Sidewall spacers 112 are disposed adjacent to the gate electrode stack106 and over only a portion of the source and drain regions 110.

Referring to FIGS. 1B and 1C, the portion of the source and drainregions 110 under the sidewall spacers 112 has a height (H2) and a width(W2) greater than a height (H1) and a width (W1) of the channel region108 of the semiconductor body 104. The heights H1 and H2 are defined asthe height of the respective portion of the semiconductor body 104 thatis above an isolation layer 114, as depicted in FIGS. 1B and 1C.

Referring to FIG. 1A, in an embodiment, a portion of the source anddrain regions 110 not under the sidewall spacers 112 has a height and awidth (W3) greater than the height (H2) and the width (W2) of theportion of the source and drain regions 110 under the sidewall spacers112, e.g., W3>W2. Alternatively, in another embodiment, a portion of thesource and drain regions 110 not under the sidewall spacers 112 has aheight and a width (W3) approximately the same as the height (H2) andthe width (W2) of the portion of the source and drain regions 110 underthe sidewall spacers 112, e.g., W3=W2.

In an embodiment, at least a portion of the source and drain regions 110is an embedded portion of the source and drain regions 110. That is, informing the source and drain regions 110, a portion of an originalsemiconductor body 104 is removed and replaced, e.g., by epitaxialgrowth, with new portions of the semiconductor body 104. For example, inone such embodiment, the embedded portion of the source and drainregions 110 is composed of a semiconductor material different than thatof the channel region 108. In one embodiment, the embedded portion doesnot include the portion of the source and drain regions 110 under thesidewall spacers 112. In another embodiment, the embedded portionincludes at least part of, and possibly all of, the portion of thesource and drain regions 110 under the sidewall spacers 112.

In an embodiment, referring to FIGS. 1B and 1C, the substrate 102 is acrystalline substrate, and the semiconductor body 104 (e.g., channelregion 108 in FIG. 1B and source and drain regions 110 in FIG. 1C) iscontinuous with the crystalline substrate 102. That is, thesemiconductor body 104 is formed from a bulk substrate. In analternative embodiment (not shown), a dielectric layer is disposedbetween the semiconductor body and the substrate, and the semiconductorbody is discontinuous with the substrate, e.g., as would be the case fora silicon-on-insulator (SOI) substrate.

In an embodiment, the channel region 108 has a height (H1) approximatelyin the range of 30-50 nanometers and a width (W1) approximately in therange of 10-30 nanometers. In that embodiment, the height (H1) of thechannel region 108 is approximately 1-2 nanometers less than the height(H2) of the portion of the source and drain regions 110 under thesidewall spacers 112. Also, the width (W1) of the channel region 108 isapproximately 2-4 nanometers less than the width (W2) of the portion ofthe source and drain regions 110 under the sidewall spacers 112. In anembodiment, the height (H2) of the portion of the source and drainregions 110 under the sidewall spacers 112 is approximately 1-7% greaterthan the height (H1) of the channel region 108. In that embodiment, thewidth (W2) of the portion of the source and drain regions 110 under thesidewall spacers 112 is approximately 6-40% greater than the width (W1)of the channel region 108.

Possible embodiments for the semiconductor device 100 in FIGS. 1A-1C aredescribed below. In a first example, FIG. 2A illustrates a plan view ofa semiconductor device having a necked semiconductor body, in accordancewith an embodiment of the present invention. Referring to FIG. 2A, thechannel region 108 is coupled to the portion of the source and drainregions 110 under the sidewall spacers 112 by a step feature 120. Thegate electrode stack 106 is depicted as dashed lines to providetransparency for the underlying channel region 108. Also, the option tohave a larger size of the portions of the source and drain regions 110not under the spacers 112 is depicted by long dashes around the sourceand drain regions 110.

In a second example, FIG. 2B illustrates a plan view of anothersemiconductor device having a necked semiconductor body, in accordancewith another embodiment of the present invention. Referring to FIG. 2B,the channel region 108 is coupled to the portion of the source and drainregions 110 under the sidewall spacers 112 by a facet feature 130. Thegate electrode stack 106 is depicted as dashed lines to providetransparency for the underlying channel region 108. Also, the option tohave a larger size of the portions of the source and drain regions 110not under the spacers 112 is depicted by long dashes around the sourceand drain regions 110.

In a third example, FIG. 2C illustrates a plan view of anothersemiconductor device having a necked semiconductor body, in accordancewith another embodiment of the present invention. Referring to FIG. 2C,the channel region 108 is coupled to the portion of the source and drainregions 110 under the sidewall spacers 112 by a rounded corner feature140. The gate electrode stack 106 is depicted as dashed lines to providetransparency for the underlying channel region 108. Also, the option tohave a larger size of the portions of the source and drain regions 110not under the spacers 112 is depicted by long dashes around the sourceand drain regions 110.

Thus, referring again to FIGS. 2B and 2C, in an embodiment, the channelregion 104 is coupled to the portion of the source and drain regions 110under the sidewall spacers 112 by a graded feature (e.g., 120 or 140).In an embodiment, the graded feature reduces overlap capacitance andspreading resistance during operating of the semiconductor device 110.

In an embodiment, as described in greater detail below in associationwith process flows 600 and 700, the semiconductor device 100 is disposedabove the same substrate 102 as a second semiconductor device having achannel region. In that embodiment, the narrowest width of the channelregion of the second semiconductor device is greater than the narrowestwidth (e.g., W1) of the channel region 108 of the semiconductor device100.

Semiconductor device 100 may be any semiconductor device incorporating agate, a channel region and a pair of source/drain regions. In anembodiment, semiconductor device 100 is one such as, but not limited to,a MOS-FET or a Microelectromechanical System (MEMS). In one embodiment,semiconductor device 100 is a three-dimensional MOS-FET and is anisolated device or is one device in a plurality of nested devices. Aswill be appreciated for a typical integrated circuit, both N- andP-channel transistors may be fabricated on a single substrate to form aCMOS integrated circuit.

Substrate 102 and, hence, semiconductor body 104 may be composed of asemiconductor material that can withstand a manufacturing process and inwhich charge can migrate. In an embodiment, the substrate 102 is a bulksubstrate, and the semiconductor body 104 is continuous with the bulksubstrate 102. In an embodiment, substrate 102 is composed of acrystalline silicon, silicon/germanium or germanium layer doped with acharge carrier, such as but not limited to phosphorus, arsenic, boron ora combination thereof. In one embodiment, the concentration of siliconatoms in substrate 102 is greater than 97% or, alternatively, theconcentration of dopant atoms is less than 1%. In another embodiment,substrate 102 is composed of an epitaxial layer grown atop a distinctcrystalline substrate, e.g. a silicon epitaxial layer grown atop aboron-doped bulk silicon mono-crystalline substrate. Substrate 102 mayalso include an insulating layer disposed in between a bulk crystalsubstrate and an epitaxial layer to form, for example, asilicon-on-insulator substrate. In such an example, the semiconductorbody 104 may be an isolated semiconductor body. In an embodiment, theinsulating layer is composed of a material such as, but not limited to,silicon dioxide, silicon nitride, silicon oxy-nitride or a high-kdielectric layer. Substrate 102 may alternatively be composed of a groupIII-V material. In an embodiment, substrate 102 is composed of a III-Vmaterial such as, but not limited to, gallium nitride, galliumphosphide, gallium arsenide, indium phosphide, indium antimonide, indiumgallium arsenide, aluminum gallium arsenide, indium gallium phosphide,or a combination thereof. Semiconductor body 104 may be composed ofmultiple semiconductor materials, each of which may include additionaldoping atoms. In one embodiment, substrate 102 is composed ofcrystalline silicon and the charge-carrier dopant impurity atoms are onesuch as, but not limited to, boron, arsenic, indium or phosphorus. Inanother embodiment, substrate 102 is composed of a III-V material andthe charge-carrier dopant impurity atoms are ones such as, but notlimited to, carbon, silicon, germanium, oxygen, sulfur, selenium ortellurium. In another embodiment, the semiconductor body 104 is undopedor only lightly doped. Additionally, halo doping, often used inconventional device fabrication, may in one embodiment be eliminated inthe fabrication of semiconductor device 100. It is to be understoodthat, in an embodiment, the material of the semiconductor body 104 isdifferent from the material of the substrate 102.

In another embodiment, the semiconductor device 100 is a non-planardevice such as, but not limited to, a fin-FET or a tri-gate device. Insuch an embodiment, the semiconductor body 104 is composed of or isformed from a three-dimensional body. In one such embodiment, the gateelectrode stack 106 surrounds at least a top surface and a pair ofsidewalls of the three-dimensional body. In another embodiment, thesemiconductor body 104 is made to be a discrete three-dimensional body,such as in a nanowire device. In one such embodiment, the gate electrodestack 106 completely surrounds a portion of the semiconductor body 104.

Gate electrode stack 106 may include a gate electrode and an underlyinggate dielectric layer. In an embodiment, the gate electrode of gateelectrode stack 106 is composed of a metal gate and the gate dielectriclayer is composed of a high-K material. For example, in one embodiment,the gate dielectric layer is composed of a material such as, but notlimited to, hafnium oxide, hafnium oxy-nitride, hafnium silicate,lanthanum oxide, zirconium oxide, zirconium silicate, tantalum oxide,barium strontium titanate, barium titanate, strontium titanate, yttriumoxide, aluminum oxide, lead scandium tantalum oxide, lead zinc niobate,or a combination thereof. Furthermore, a portion of gate dielectriclayer may include a layer of native oxide formed from the top few layersof the semiconductor body 104. In an embodiment, the gate dielectriclayer is composed of a top high-k portion and a lower portion composedof an oxide of a semiconductor material. In one embodiment, the gatedielectric layer is composed of a top portion of hafnium oxide and abottom portion of silicon dioxide or silicon oxy-nitride.

In one embodiment, the gate electrode is composed of a metal layer suchas, but not limited to, metal nitrides, metal carbides, metal silicides,metal aluminides, hafnium, zirconium, titanium, tantalum, aluminum,ruthenium, palladium, platinum, cobalt, nickel or conductive metaloxides. In a specific embodiment, the gate electrode is composed of anon-workfunction-setting fill material formed above a metalworkfunction-setting layer. In an embodiment, the gate electrode iscomposed of a P-type material. In another embodiment, the gate electrodeis composed of an N-type material. In another embodiment, the gateelectrode is composed of a mid-gap material. In a specific suchembodiment, the corresponding channel region is undoped or is onlylightly doped.

In an embodiment, the sidewall spacers 112 are composed of an insulativedielectric material such as, but not limited to, silicon dioxide,silicon carbide, silicon oxy-nitride or silicon nitride Likewise, thedielectric layer 114 may be composed of an insulative dielectricmaterial such as, but not limited to, silicon dioxide, silicon carbide,silicon oxy-nitride or silicon nitride.

Methods of forming devices such as those described above are alsocontemplated within the spirit and scope of embodiments of the presentinvention. In a first example, FIG. 3 illustrates a process flow 300 ina method of fabricating a semiconductor device having a neckedsemiconductor body, in accordance with an embodiment of the presentinvention.

Referring to part A of process flow 300, a thick fin 302 is formed, asacrificial gate 304 is patterned, gate spacers 306 are formed byblanket deposition and subsequent etching, and source-drain regions 308are formed. Additionally, an interlayer-dielectric film 310 may bedeposited and polished to expose the sacrificial gate 304. Referring topart B of process flow 300, the sacrificial gate 304 is removed and thethick fin 302 is etched to form a thinned fin 312 with a reducedthickness, e.g., reduced by an amount approximately in the range of 1-5nanometers. Referring to part C of process flow 300, a permanent gatestack 320 is formed over the thinned fin 312. For example, a high-k gatedielectric layer and a metal gate electrode may be formed. In anembodiment, the thinned fin 312 provides improved short channel effects,while the wider portion of the source and drain regions 308 under thespacers 306 aid in reducing external resistance.

The sacrificial gate 304 is, in an embodiment, composed of a materialsuitable for removal at the replacement gate operation. In oneembodiment, sacrificial gate 304 is composed of polycrystalline silicon,amorphous silicon, silicon dioxide, silicon nitride, or a combinationthereof. In another embodiment, a protective capping layer (not shown),such as a silicon dioxide or silicon nitride layer, is formed abovesacrificial gate 304 is. In an embodiment, an underlying dummy gatedielectric layer (also not shown) is included. In an embodiment,sacrificial gate 304 is includes the sidewall spacers 306, which may becomposed of a material suitable to ultimately electrically isolate apermanent gate structure from adjacent conductive contacts. For example,in one embodiment, the spacers 306 are composed of a dielectric materialsuch as, but not limited to, silicon dioxide, silicon oxy-nitride,silicon nitride, or carbon-doped silicon nitride.

In an embodiment, sacrificial gate 304 is removed by a dry etch or wetetch process. In one embodiment, sacrificial gate 304 is composed ofpolycrystalline silicon or amorphous silicon and is removed with a dryetch process using SF₆. In another embodiment, sacrificial gate 304 iscomposed of polycrystalline silicon or amorphous silicon and are removedwith a wet etch process using aqueous NH₄OH or tetramethylammoniumhydroxide. In one embodiment, sacrificial gate 304 is composed ofsilicon nitride and are removed with a wet etch using aqueous phosphoricacid.

The fin 302 may be thinned to form 312 by any suitable technique thatremoves a portion of fin 302 without detrimentally impacting othersemiconductor features that are present, such as by using a dry etch ora wet etch process. In one embodiment, fin 302 is thinned to form 312 byusing a dry plasma etch using NF₃, HBr, SF₆/Cl or Cl₂. In anotherembodiment, wet etch process is used.

In a second example, FIG. 4 illustrates a process flow 400 in a methodof fabricating a semiconductor device having a necked semiconductorbody, in accordance with an embodiment of the present invention.Referring to part A of process flow 400, a thin fin 412 is formed, asacrificial gate 404 is patterned, and thin source-drain regions 408 areformed. Referring to part B of process flow 400, gate spacers 406 areformed by blanket deposition and subsequent etching, and thick sourceand drain regions 418 are formed, e.g., by epitaxial growth.Additionally, an interlayer-dielectric film 410 may be deposited andpolished to expose the sacrificial gate 404. The sacrificial gate 404 isthen removed, as depicted in part B. Referring to part C of process flow400, a permanent gate stack 420 is formed over the thin fin 412. Forexample, a high-k gate dielectric layer and a metal gate electrode maybe formed. In an embodiment, the thin fin 412 provides improved shortchannel effects, while the wider portion of the source and drain regions408/418 under the spacers 406 aid in reducing external resistance.Sacrificial gate formation and replacement may be performed as describedabove in association with process flow 300.

Thus, in an embodiment, a method of fabricating a semiconductor deviceincludes forming a semiconductor body above a substrate. A gateelectrode stack is formed over a portion of the semiconductor body todefine a channel region in the semiconductor body under the gateelectrode stack and source and drain regions in the semiconductor bodyon either side of the gate electrode stack. Sidewall spacers are formedadjacent to the gate electrode stack and over only a portion of thesource and drain regions. The portion of the source and drain regionsunder the sidewall spacers has a height and a width greater than aheight and a width of the channel region of the semiconductor body.

In one such embodiment, forming the gate electrode stack includesforming a sacrificial gate electrode stack, removing the sacrificialgate electrode stack, and forming a permanent gate electrode stack. Inthat embodiment, forming the channel region includes thinning a portionof the semiconductor body exposed subsequent to removing the sacrificialgate electrode stack and prior to forming the permanent gate electrodestack, e.g., as described in association with process flow 300. Inanother such embodiment, forming the gate electrode stack includesforming a sacrificial gate electrode stack, removing the sacrificialgate electrode stack, and forming a permanent gate electrode stack. Inthat embodiment, forming the source and drain regions includes expandinga portion of the semiconductor body exposed prior to removing thesacrificial gate electrode stack, e.g., as described in association withprocess flow 400.

FIG. 5A includes a plot 500A of drive current gain (as % Idsat gain) asa function of silicon channel thickness (in microns) of a semiconductordevice having a necked semiconductor body versus a semiconductor devicewithout a necked semiconductor body, in accordance with an embodiment ofthe present invention. FIG. 5B includes a plot 500B of drive currentgain (as % Idlin gain) as a function of silicon channel thickness (inmicrons) of a semiconductor device having a necked semiconductor bodyversus a semiconductor device without a necked semiconductor body, inaccordance with an embodiment of the present invention. Referring toplots 500 A and 500B, a fin formed by up front silicon width (Wsi)definition is compared against a fin with thinned silicon width (Wsi) asdefined during a replacement gate operation, e.g., as described inassociation with process flow 300. The plots reveal the expected drivecurrent gain for the thinned fin device.

In a second aspect, methods of forming semiconductor bodies of varyingwidth are provided. Such a process may enable formation of different finwidths within the same die. Using wider fin width devices for highperformance application and lower fin width devices for low power (lowstandby leakage) applications may thus be achieved on the same die.

In a first example, FIG. 6 illustrates a process flow 600 in a method offabricating semiconductor devices having with semiconductor bodies ofvarying width, in accordance with an embodiment of the presentinvention.

Referring to part A of process flow 600, hardmask 603A/603B formationabove a substrate 602, e.g., above a crystalline silicon substrate, forultimate fin formation includes deposition and patterning of a hardmasklayer. The patterned hardmask layer 603A/603B includes regions 604 forultimate thin fin formation and region 606 for ultimate thick finformation. Referring to part B of process flow 600, the fins that willremain wider (e.g., in region 606) are blocked with resist layer 608 andthe exposed hardmask 603A is etched to reduce the width of the lines.Referring to part C of process flow 600, the resist layer 608 is thenremoved, e.g. including an ash process, and the new hardmask pattern603A/603B is transferred into the substrate 602 to form the fins 610Aand 610B. Alternatively, in an embodiment, the additional lithographyfin thinning may be performed after the fins are etched into thesubstrate and prior to patterning of a sacrificial gate. In anembodiment, hardmask regions 603A/603B are first formed by a spacerpatterning flow, which may be used to effectively double the pitch ofthe lithographic process used to form the features. Process flow 600preserves the pitch of the spacer patterning flow.

Thus, in an embodiment, a method of fabricating a semiconductor deviceincludes forming a hardmask pattern above a substrate. The hardmaskpattern includes a first region of fin forming features, each of a firstwidth. The hardmask pattern also includes a second region of fin formingfeatures, each of a second width approximately equal to the first width.Subsequently, a resist layer is formed and patterned to cover the secondregion and expose the first region. Subsequently, the fin formingfeatures of the first region are etched to form thinned fin formingfeatures, each of a third width less than the second width.Subsequently, the resist layer is removed. Subsequently, the hardmaskpattern is transferred to the substrate to form a first region of fins,each of the third width, and to form a second region of fins, each ofthe second width. Subsequently, semiconductor devices are formed fromthe fins of the first and second regions. In one such embodiment, thesubstrate is a single-crystalline silicon substrate, and transferringthe hardmask pattern to the substrate includes forming singlecrystalline silicon fins.

In a second example, FIG. 7 illustrates a process flow 700 in a methodof fabricating semiconductor devices having with semiconductor bodies ofvarying width, in accordance with an embodiment of the presentinvention.

Referring to part A of process flow 700, hardmask 703A/703B formationabove a substrate 702, e.g., above a crystalline silicon substrate, forfin formation includes deposition and patterning of a hardmask layer.The patterned hardmask layer 703A/703B includes regions 704 for thin finformation and region 706 for thick fin formation. The hardmask pattern703A/703B is the transferred into the substrate 702 to formcorresponding fins. Sacrificial gate patterning and extension source anddrain formation may then be performed. Also, an inter-layer dielectricmaterial may be deposited and the polished to reveal the sacrificialgates. The sacrificial gates are then removed. Referring to part B ofprocess flow 700, the fins 710B that will remain wider (e.g., in region706) are blocked with resist layer 708. A fin thinning etch is used toreduce the fin width of the fins 710A. Referring to part C of processflow 700, the resist layer 708 is removed, e.g. including an ashprocess, and standard device fabrication techniques may be performedusing thinner fins 710A and wider fins 710B. In an embodiment, hardmaskregions 703A/703B are first formed by a spacer patterning flow, whichmay be used to effectively double the pitch of the lithographic processused to form the features. Process flow 700 preserves the pitch of thespacer patterning flow.

Thus, in an embodiment, a method of fabricating a semiconductor deviceincludes forming a hardmask pattern above a substrate. The hardmaskpattern includes a first region of fin forming features, each of a firstwidth. The hardmask pattern also includes a second region of fin formingfeatures, each of a second width approximately equal to the first width.Subsequently, the hardmask pattern is transferred to the substrate toform a first region of fins, each of the first width, and to form asecond region of fins, each of the second width. Subsequently, a resistlayer is formed and patterned to cover the second region of fins and toexpose the first region of fins. Subsequently, the fins of the firstregion are etched to form thinned fins, each of a third width less thanthe second width. Subsequently, the resist layer is removed.Subsequently, semiconductor devices are formed from the fins of thefirst and second regions. In one such embodiment, the substrate is asingle-crystalline silicon substrate, and transferring the hardmaskpattern to the substrate includes forming single crystalline siliconfins.

The processes described herein may be used to fabricate one or aplurality of semiconductor devices. The semiconductor devices may betransistors or like devices. For example, in an embodiment, thesemiconductor devices are a metal-oxide semiconductor (MOS) transistorsfor logic or memory, or are bipolar transistors. Also, in an embodiment,the semiconductor devices have a three-dimensional architecture, such asa trigate device, an independently accessed double gate device, or aFIN-FET.

FIG. 8 illustrates a computing device 800 in accordance with oneimplementation of the invention. The computing device 800 houses a board802. The board 802 may include a number of components, including but notlimited to a processor 804 and at least one communication chip 806. Theprocessor 804 is physically and electrically coupled to the board 802.In some implementations the at least one communication chip 806 is alsophysically and electrically coupled to the board 802. In furtherimplementations, the communication chip 806 is part of the processor804.

Depending on its applications, computing device 800 may include othercomponents that may or may not be physically and electrically coupled tothe board 802. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 806 enables wireless communications for thetransfer of data to and from the computing device 800. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 806 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 800 may include a plurality ofcommunication chips 806. For instance, a first communication chip 806may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 806 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 804 of the computing device 800 includes an integratedcircuit die packaged within the processor 804. In some implementationsof the invention, the integrated circuit die of the processor includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of the invention. The term “processor” may refer toany device or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 806 also includes an integrated circuit diepackaged within the communication chip 806. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as MOS-FETtransistors built in accordance with implementations of the invention.

In further implementations, another component housed within thecomputing device 800 may contain an integrated circuit die that includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of the invention.

In various implementations, the computing device 800 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 800 may be any other electronic device that processes data.

Thus, semiconductor devices having necked semiconductor bodies andmethods of forming semiconductor bodies of varying width have beendisclosed. In an embodiment, a semiconductor device includes asemiconductor body disposed above a substrate. A gate electrode stack isdisposed over a portion of the semiconductor body to define a channelregion in the semiconductor body under the gate electrode stack. Sourceand drain regions are defined in the semiconductor body on either sideof the gate electrode stack. Sidewall spacers are disposed adjacent tothe gate electrode stack and over only a portion of the source and drainregions. The portion of the source and drain regions under the sidewallspacers has a height and a width greater than a height and a width ofthe channel region of the semiconductor body. In one embodiment, thesemiconductor device is disposed above the same substrate as a secondsemiconductor device having a channel region, and the narrowest width ofthe channel region of the second semiconductor device is greater thanthe narrowest width of the channel region of the semiconductor device.

What is claimed is:
 1. A semiconductor device, comprising: asemiconductor body disposed above a substrate; a gate electrode stackdisposed over a portion of the semiconductor body to define a channelregion in the semiconductor body under the gate electrode stack andsource and drain regions in the semiconductor body on either side of thegate electrode stack; and sidewall spacers disposed adjacent to the gateelectrode stack and over only a portion of the source and drain regions,wherein the portion of the source and drain regions under the sidewallspacers has a height and a width greater than a height and a width ofthe channel region of the semiconductor body.
 2. The semiconductordevice of claim 1, wherein a portion of the source and drain regions notunder the sidewall spacers has a height and a width greater than theheight and the width of the portion of the source and drain regionsunder the sidewall spacers.
 3. The semiconductor device of claim 1,wherein a portion of the source and drain regions not under the sidewallspacers has a height and a width approximately the same as the heightand the width of the portion of the source and drain regions under thesidewall spacers.
 4. The semiconductor device of claim 1, wherein atleast a portion of the source and drain regions is an embedded portionof the source and drain regions.
 5. The semiconductor device of claim 4,wherein the embedded portion of the source and drain regions comprise asemiconductor material different than the channel region.
 6. Thesemiconductor device of claim 1, wherein the substrate is a crystallinesubstrate, and the semiconductor body is continuous with the crystallinesubstrate.
 7. The semiconductor device of claim 1, wherein a dielectriclayer is disposed between the semiconductor body and the substrate, andthe semiconductor body is discontinuous with the substrate.
 8. Thesemiconductor device of claim 1, wherein the channel region has a heightapproximately in the range of 30-50 nanometers and a width approximatelyin the range of 10-30 nanometers, the height of the channel region isapproximately 1-2 nanometers less than the height of the portion of thesource and drain regions under the sidewall spacers, and the width ofthe channel region is approximately 2-4 nanometers less than the widthof the portion of the source and drain regions under the sidewallspacers.
 9. The semiconductor device of claim 1, wherein the height ofthe portion of the source and drain regions under the sidewall spacersis approximately 1-7% greater than the height of the channel region, andthe width of the portion of the source and drain regions under thesidewall spacers is approximately 6-40% greater than the width of thechannel region.
 10. The semiconductor device of claim 1, wherein thechannel region is coupled to the portion of the source and drain regionsunder the sidewall spacers by a step feature.
 11. The semiconductordevice of claim 1, wherein the channel region is coupled to the portionof the source and drain regions under the sidewall spacers by a gradedfeature.
 12. The semiconductor device of claim 11, wherein the gradedfeature comprises a facet.
 13. The semiconductor device of claim 11,wherein the graded feature comprises a rounded corner.
 14. Thesemiconductor device of claim 11, wherein the graded feature reducesoverlap capacitance and spreading resistance during operating of thesemiconductor device.
 15. The semiconductor device of claim 1, whereinthe semiconductor device is disposed above the same substrate as asecond semiconductor device having a channel region, and wherein thenarrowest width of the channel region of the second semiconductor deviceis greater than the narrowest width of the channel region of thesemiconductor device.
 16. A method of fabricating a semiconductordevice, the method comprising: forming a semiconductor body above asubstrate; forming a gate electrode stack over a portion of thesemiconductor body to define a channel region in the semiconductor bodyunder the gate electrode stack and source and drain regions in thesemiconductor body on either side of the gate electrode stack; andforming sidewall spacers adjacent to the gate electrode stack and overonly a portion of the source and drain regions, wherein the portion ofthe source and drain regions under the sidewall spacers has a height anda width greater than a height and a width of the channel region of thesemiconductor body.
 17. The method of claim 16, wherein forming the gateelectrode stack comprises forming a sacrificial gate electrode stack,removing the sacrificial gate electrode stack, and forming a permanentgate electrode stack, and wherein forming the channel region comprisesthinning a portion of the semiconductor body exposed subsequent toremoving the sacrificial gate electrode stack and prior to forming thepermanent gate electrode stack.
 18. The method of claim 16, whereinforming the gate electrode stack comprises forming a sacrificial gateelectrode stack, removing the sacrificial gate electrode stack, andforming a permanent gate electrode stack, and wherein forming the sourceand drain regions comprises expanding a portion of the semiconductorbody exposed prior to removing the sacrificial gate electrode stack. 19.A method of fabricating a semiconductor device, the method comprising:forming a hardmask pattern above a substrate, the hardmask patterncomprising a first region of fin forming features, each of a firstwidth, and the hardmask pattern also comprising a second region of finforming features, each of a second width approximately equal to thefirst width; and, subsequently, forming and patterning a resist layer tocover the second region and expose the first region; and, subsequently,etching the fin forming features of the first region to form thinned finforming features, each of a third width less than the second width; and,subsequently, removing the resist layer; and, subsequently, transferringthe hardmask pattern to the substrate to form a first region of fins,each of the third width, and to form a second region of fins, each ofthe second width; and, subsequently, forming semiconductor devices fromthe fins of the first and second regions.
 20. The method of claim 19,wherein the substrate is a single-crystalline silicon substrate, andwherein transferring the hardmask pattern to the substrate comprisesforming single crystalline silicon fins.
 21. A method of fabricating asemiconductor device, the method comprising: forming a hardmask patternabove a substrate, the hardmask pattern comprising a first region of finforming features, each of a first width, and the hardmask pattern alsocomprising a second region of fin forming features, each of a secondwidth approximately equal to the first width; and, subsequently,transferring the hardmask pattern to the substrate to form a firstregion of fins, each of the first width, and to form a second region offins, each of the second width; and, subsequently, forming andpatterning a resist layer to cover the second region of fins and exposethe first region of fins; and, subsequently, etching the fins of thefirst region to form thinned fins, each of a third width less than thesecond width; and, subsequently, removing the resist layer; and,subsequently, forming semiconductor devices from the fins of the firstand second regions.
 22. The method of claim 21, wherein the substrate isa single-crystalline silicon substrate, and wherein transferring thehardmask pattern to the substrate comprises forming single crystallinesilicon fins.